US7606493B2 - Optical waveguide and optical multiplexer-demultiplexer - Google Patents
Optical waveguide and optical multiplexer-demultiplexer Download PDFInfo
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- US7606493B2 US7606493B2 US10/949,657 US94965704A US7606493B2 US 7606493 B2 US7606493 B2 US 7606493B2 US 94965704 A US94965704 A US 94965704A US 7606493 B2 US7606493 B2 US 7606493B2
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/12007—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer
- G02B6/12009—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer comprising arrayed waveguide grating [AWG] devices, i.e. with a phased array of waveguides
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/12007—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
- G02B6/124—Geodesic lenses or integrated gratings
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
- G02B6/2938—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM
Definitions
- the present invention relates to an optical waveguide and an optical multiplexer-demultiplexer and, in particular, to an optical demultiplexing waveguide which can classify optical signals constituted by those having a plurality of wavelengths into groups each having a single wavelength, an optical multiplexing waveguide which can compose optical signals constituted by those having a plurality of wavelengths and an optical multiplexer-demultiplexer.
- the present invention likewise relates to an optical multiplexer-demultiplexer used in the wavelength division multiplexing transmission wherein the wavelength range is about several tens of nanometers.
- WDM wavelength division multiplexing
- DWDM dense wavelength division multiplexing
- the coarse wavelength division multiplexing (CWDM) transmission technique in which the wavelength range used is expanded to a level of not less than 20 nm in order to cope with such a fluctuation in wavelength on the order of about 10 nm.
- CWDM coarse wavelength division multiplexing
- the use of a temperature control means such as a laser can be omitted and therefore, this may reduce the cost required for communication.
- an optical multiplexer for composing or coupling a plurality of optical signals having different wavelengths and a demultiplexer for classifying such signals into groups each having a single wavelength in order to realize such WDM transmission.
- optical multiplexer-demultiplexer which can cope with a wide wavelength fluctuation like one for the CWDM transmission
- optical multiplexer-demultiplexer which makes use of an optical waveguide and a diffraction grating such as that disclosed in Applied Optics, 1982, 21: 2195.
- This optical multiplexer-demultiplexer comprising the combination of these two components permits the reduction of the number of parts to be used and the miniaturization of this device.
- a method for realizing the CWDM transmission there has been known, for instance, one which comprises the step of demultiplexing light rays using a plurality of multilayered thin film filters, each of which can pass light rays of a desired wavelength therethrough, in the number corresponding to that of the wavelengths of these light rays.
- the optical demultiplexer used in this method comprises a wavelength filter consisting of about 100 thin layers, whose thickness is highly precisely controlled, a collimating lens and a fiber which are assembled in such a manner that the optical axes thereof are in good agreement with one another.
- the conventional optical multiplexer-demultiplexer which makes use of an AWG can simply cope with the narrow wavelength fluctuation of not more than 0.1 nm and therefore, it cannot perform any optical multiplexing or coupling and demultiplexing operation when the wavelength fluctuation is on the order of 10 nm like the CWDM transmission.
- the optical multiplexer-demultiplexer for the CWDM transmission should satisfy the requirement for morphological characteristics such as the flat top-shaped characteristics as shown in the attached FIG. 9 , in which the transmission loss does not vary even for the wavelength fluctuation of about 10 nm.
- the conventional optical multiplexer-demultiplexer which made use of a diffraction grating showed cone-shaped characteristics as disclosed in the foregoing article: Applied Optics, 1982, 21: 2195, in which the transmission loss increased in proportion to the wavelength fluctuation.
- a multiplexing and demultiplexing method using a multilayered thin film filter it is necessary to use a plurality of multilayered thin film filters, which are quite expensive and whose mass-production is quite difficult, in proportion to the number of wavelengths and it is also needed to highly precisely position the same with respect to a precise lens and/or an optical fiber.
- the resulting device is quite expensive.
- a problem arises such that the productivity thereof is likewise low and accordingly, the mass production thereof is quite difficult.
- an optical multiplexer-demultiplexer which makes use of an optical waveguide and a diffraction grating
- the optical waveguide used has a large absolute value (hereunder referred to as “birefringence index”) of the difference between the refractive index (nTE) of the core layer of the optical waveguide in the direction parallel to the plane of the film and that (nTM) of the core layer thereof in the direction perpendicular to the plane of the film, a problem arises such that the wavelength of the outputted (or outgoing) signal light varies depending on the polarization direction of the inputted signal light.
- the optical multiplexer-demultiplexer for the CWDM transmission should perform multiplexing and demultiplexing operations even when the wavelength fluctuation in the outputted signal light is at least 10 nm.
- the wavelength fluctuation in the light oscillated from a laser as a light source may be at least 5 nm due to the dispersion of the laser produced and the temperature change in the environment in which the laser is used and therefore, the wavelength fluctuation due to the birefringence index should be not more than 5 nm.
- the refractive index n of the film is found to be 1.5291 and the birefringence index ⁇ n thereof is found to be 0.009 at a wavelength used of 1300 nm. From the foregoing, the wavelength fluctuation ⁇ is found to fall within the range of from about 7 to 8 nm and this becomes a serious obstacle in practical applications.
- optical waveguides and optical multiplexer-demultiplexers there are provided the following optical waveguides and optical multiplexer-demultiplexers:
- An optical waveguide which comprises a core 4 for incident light and a core 5 for outgoing light, wherein the width of the core 5 for outgoing light is more than 1.5 times that of the core 4 for incident light.
- optical waveguide wherein it further comprises at least one core for alignment.
- An optical multiplexer-demultiplexer which makes use of an optical waveguide serving as an optical path and a diffraction grating for demultiplexing and focusing light, wherein the absolute value of the difference between the refractive index (nTE) of the core layer of the optical waveguide in the direction parallel to the plane of the film and that (nTM) of the core layer thereof in the direction perpendicular to the plane of the film is not more than 0.007 at the wavelength used.
- the optical multiplexer-demultiplexer as set forth in any one of the foregoing items 6 to 10, wherein the optical waveguide and a substrate supporting the waveguide are made of resins.
- FIG. 1( a ) is a schematic side view of an optical multiplexer-demultiplexer described in Example 1 according to the present invention and FIG. 1( b ) is a cross sectional view thereof taken along the line A-A′ in FIG. 1( a ).
- FIG. 2( a ) is a schematic side view of an optical multiplexer-demultiplexer described in Example 1 according to the present invention and FIG. 2( b ) is a cross sectional view thereof taken along the line A-A′ in FIG. 2( a ).
- FIG. 3( a ) is a schematic side view of an optical multiplexer-demultiplexer described in Example 1 according to the present invention and FIG. 3( b ) is a cross sectional view thereof taken along the line A-A′ in FIG. 3( a ).
- FIG. 4( a ) is a schematic side view of an optical multiplexer-demultiplexer described in Example 2 according to the present invention and FIG. 4( b ) is a cross sectional view thereof taken along the line A-A′ in FIG. 4( a ).
- FIG. 5( a ) is a schematic side view of an optical multiplexer-demultiplexer described in Example 2 according to the present invention and FIG. 5( b ) is a cross sectional view thereof taken along the line A-A′ in FIG. 5( a ).
- FIG. 6( a ) is a schematic side view of an optical multiplexer-demultiplexer described in Example 3 according to the present invention and FIG. 6( b ) is a cross sectional view thereof taken along the line A-A′ in FIG. 6( a ).
- FIG. 7( a ) is a schematic side view of an optical multiplexer-demultiplexer described in Example 3 according to the present invention and FIG. 7( b ) is a cross sectional view thereof taken along the line A-A′ in FIG. 7( a ).
- FIG. 8( a ) is a schematic side view of an optical multiplexer-demultiplexer described in Example 4 according to the present invention and FIG. 8( b ) is a cross sectional view thereof taken along the line A-A′ in FIG. 8( a ).
- FIG. 9 is a diagram showing the optical demultiplexing characteristics observed for a multiplexer-demultiplexer for the CWDM transmission.
- FIG. 10( a ) is a block diagram showing an optical multiplexer-demultiplexer according to an embodiment of the present invention
- FIG. 10( b ) is a cross sectional view thereof taken along the line A-A′ in FIG. 10( a )
- FIG. 10( c ) is a cross sectional view thereof taken along the line B-B′ in FIG. 10( a ).
- FIG. 11 is a diagram showing the optical demultiplexing characteristics observed for the optical multiplexer-demultiplexer shown in FIG. 10 .
- an optical waveguide detailed below.
- the invention provides an optical waveguide which comprises a core 4 for incident light and a core 5 for outputted or outgoing light, wherein the width of the core 5 for outgoing light is more than 1.5 times, preferably 2 to 20 times, more preferably 2 to 10 times and most preferably 3 to 8 times that of the core 4 for incident light.
- the width of the core 4 for incident light preferably ranges from 3 to 10 ⁇ m and that of the core for outgoing light preferably ranges from 15 to 50 ⁇ m.
- the light incident upon the core 5 for outgoing light has a small spot shape in order to impart such flat top-shaped optical demultiplexing characteristics as those shown in FIG. 9 to an optical multiplexer-demultiplexer and, to this end, the optical waveguide used is preferably so designed that the light propagating through the core 4 for incident light is in a single mode.
- the width of the core herein used means the width of each core when a plurality of cores are used.
- the resulting optical waveguide shows such a flat transmission loss as that shown in FIG. 9 only for a narrow wavelength fluctuation and cannot cope with the fluctuation over a wide wavelength range required for the CWDM transmission. If the width of the core 5 for outgoing light is greater than 20 times that of the core 4 for incident light, a problem may arise such that the resulting optical waveguide correspondingly increases in its size.
- the core diameter of the optical fiber used and the light-receiving area of a light-receiving device, upon which the outputted light is incident are increased in proportion to the large width of the core and as a result, the propagation speed of the light is limited and therefore, it may be unacceptable in the high speed transmission.
- the width of the core 5 for outgoing light is larger than that of the core 4 for incident light and therefore, it is difficult to accurately position the optical waveguide with respect to parts such as an optical fiber and/or a diffraction grating, while monitoring the intensity of the light outputted from the core 5 for outgoing light.
- the optical waveguide according to the present invention comprises a plurality of cores 4 for incident light; a plurality of cores 5 for outgoing light each having a width greater than that of the core 4 ; a diffraction grating 7 or an array optical waveguide-diffraction grating 10 , having unevenness or a refractive index distribution and accordingly, the optical waveguide can be used in an optical multiplexer-demultiplexer which can cope even with the wide wavelength fluctuation in the order of 10 nm.
- the optical waveguide of the present invention may be so designed that it comprise a plurality of cores 4 for incident light and a single core 5 for outgoing light and the resulting waveguide can be used in an optical multiplexer-demultiplexer whose surface area is reduced.
- the optical waveguide of the present invention may likewise be so designed that it comprise a single core 4 for incident light and a plurality of cores 5 for outgoing light and the resulting waveguide can be used in an optical multiplexer-demultiplexer whose surface area is reduced.
- a single mode optical fiber is used in the long distance transmission or communication exceeding the distance of 1 km.
- the optical multiplexer-demultiplexer of the present invention cannot suitably be used since the optical fiber would undergo a significant transmission loss when it is connected to the optical multiplexer-demultiplexer.
- the optical waveguide of the present invention is preferably used in an optical demultiplexing device.
- the transmission type and reflector type diffraction gratings may be used in the invention as those having unevenness or projections on the surface and used for forming an optical multiplexer-demultiplexer and the reflector type diffraction grating usable herein may be one coated with a reflection coat of, for instance, a metal for the improvement of the reflectance thereof.
- a reflection coat of, for instance, a metal for the improvement of the reflectance thereof may be one coated with a reflection coat of, for instance, a metal for the improvement of the reflectance thereof.
- the position of the diffraction grating can be optimized in such a manner that the intensity of the light outputted through the core for alignment is maximized when the diffracted light from the diffraction grating is incident upon the core for alignment.
- the optical multiplexer-demultiplexer thus completed shows flat top-shaped wavelength characteristics as shown in FIG. 9 .
- the transmission loss of light within the optical multiplexer-demultiplexer does not depend on the wavelength within the wavelength range on the order of 10 nm and the device may have characteristic properties whose tolerance is quite wide with respect to the wavelength fluctuation due to, for instance, the temperature change of a laser used.
- the absolute value of the difference between the refractive index (nTE) of the core layer of the optical waveguide in the direction parallel to the plane of the film and that (nTM) of the core layer thereof in the direction perpendicular to the plane of the film is not more than 0.007 at the wavelength used.
- an optical multiplexer-demultiplexer which makes use of an optical waveguide serving as an optical path and a diffraction grating for demultiplexing and focusing light, wherein the absolute value of the difference between the refractive index (nTE) of the core layer of the optical waveguide in the direction parallel to the plane of the film and that (nTM) of the core layer thereof in the direction perpendicular to the plane of the film is not more than 0.007 at the wavelength used.
- the wavelength fluctuation in the outputted signal light which is dependent on the polarization direction of the incident signal light, can be restricted to a level of not more than 5 nm.
- the foregoing value is a birefringence index ⁇ n as determined according to the foregoing equation (1) while the wavelength ⁇ used and the refractive index n are assumed to be 1270 to 1610 nm and 1.4 to 1.7, respectively such that the wavelength fluctuation ⁇ is not more than 5 nm.
- acrylic resins examples include acrylic resins, epoxy resins, silicone resins, SiO 2 or SiO 2 doped with at least one additive selected from, for instance, Ge, Ti and F for the control of the refractive index thereof.
- acrylic resins and SiO 2 or SiO 2 doped with at least one additive selected from, for instance, Ge, Ti and F for the control of the refractive index have an intrinsic birefringence index of not more than 0.001 and therefore, they are preferably used in a core layer of an optical waveguide.
- a ratio of the thermal expansion coefficient of the optical waveguide including the core layer (light-guiding core layer) to that of a substrate therefor is preferably not more than 30 times, more preferably not more than 20 times and most preferably not more than 10 times.
- the optical waveguide When preparing an optical waveguide comprising a light-guiding core layer using, for instance, a fluorinated polyimide, the optical waveguide has conventionally been formed on a substrate such as a silicon or quartz substrate.
- a ratio of the thermal expansion coefficient of the optical waveguide to that of the substrate is not less than 10 and therefore, a residual stress is generated in the polyimide film after the film-formation. This stress accordingly leads to the generation of a large birefringence index.
- the thermal expansion coefficient of the optical waveguide is brought close to that of the substrate or when the optical waveguide is made of a polymer, it is effective to obtain a substrate for supporting the polymeric waveguide from a resin whose thermal expansion coefficient is very close to that of the polymer used for the production of the optical waveguide.
- the birefringence index of the resulting light-guiding core layer can be reduced to a level of less than 0.001.
- the diffraction grating used in the optical multiplexer-demultiplexer according to the present invention is not restricted to any specific one, but specific examples thereof usable herein are reflector type diffraction gratings such as those provided with a metal coat of, for instance, Al and Au on the surface thereof as a reflection coat and transmission type diffraction gratings such as those obtained using, as base materials therefor, materials capable of transmitting light therethrough such as quartz and transparent plastic materials.
- an optical multiplexer-demultiplexer having such a structure that a diffraction grating is provided independent of the optical waveguide substrate, but the present invention is not restricted to these specific embodiments at all and a diffraction grating and an optical waveguide can be integrated or united.
- the alignment of elemental diffraction grating and optical waveguide can be omitted upon the packaging of the device and this accordingly permits the simplification of the steps for the production of the optical multiplexer-demultiplexer and the significant reduction of the production cost.
- FIG. 1( a ) is a side view of an optical waveguide according to the present invention
- FIG. 1( b ) is a cross sectional view thereof taken along the line A-A′ in FIG. 1( a ).
- a core 3 having a rectangular cross section is embedded in a claddingding 2 positioned on a substrate 1 ; the core 3 has a pattern comprising four cores 4 for incident light (incident cores), four cores 5 for outgoing light (outgoing cores), an incident core 8 and an outgoing core 9 for alignment and a slab-like core 6 ; and a diffraction grating 7 is arranged at the right edge of the optical waveguide.
- materials for preparing the substrate used herein may, for instance, be a glass, a semiconductor (Si or the like) or a polymeric resin.
- those for preparing the cladding 2 and the core 3 may be, for instance, SiO 2 , or SiO 2 which comprises at least one additive for controlling the refractive index of these cladding and core such as Ge, Ti and F, or a polymeric material such as a fluorinated polyimide, a silicone resin or an epoxy resin whose refractive index is adjusted.
- the diffraction grating 7 is provided, on the surface, with irregularity having a desired period and a metal such as Au or Al is coated on the surface thereof, which comes in contact with the optical waveguide, in order to reflect light rays.
- the optical multiplexer-demultiplexer When using the optical multiplexer-demultiplexer as an optical multiplexer, four kinds of light rays having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 and ⁇ 4 are incident upon four incident cores 4 respectively as shown in FIG. 2 .
- the incident light rays propagate through the incident cores 4 and the slab-like core 6 , strike on the diffraction grating 7 and each light ray is reflected by the same at an angle specified by the wavelength thereof.
- the resulting optical multiplexer-demultiplexer can operate as an optical multiplexer and as a result, the four kinds of light rays reflected by the diffraction grating 7 are externally outputted through the single outgoing core 5 .
- wavelength-multiplexed four optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 and ⁇ 4 are incident upon the predetermined incident cores 4 as shown in FIG. 3 .
- These incident light rays propagate through the incident cores 4 and further the slab-like core 6 , strike on the diffraction grating 7 and each light ray is reflected by the same at an angle specified by the wavelength thereof.
- the optical multiplexer-demultiplexer can serve as an optical demultiplexer so that the four kinds of light rays having different wavelengths reflected by the diffraction grating 7 are demultiplexed into groups each having a specific wavelength, they are thus incident upon the outgoing cores 5 having the corresponding wavelengths ⁇ 1 , ⁇ 2 , ⁇ 3 and ⁇ 4 and are externally outputted through the four corresponding outgoing cores 5 .
- the width of the outgoing core 5 is greater than that of the incident core 4 and more specifically, the width of each incident core 4 is 7 ⁇ m and that of each outgoing core 5 is 30 ⁇ m.
- an incident core 8 and an outgoing core 9 for the alignment of the diffraction grating 7 are formed in addition to the incident cores 4 and the outgoing cores 5 . They are used for accurately arranging the diffraction grating 7 at a predetermined position.
- Light rays having a wavelength of ⁇ 5 are incident upon the incident core 8 for alignment, followed by receiving the light rays reflected by the diffraction grating 7 on the outgoing core 9 for alignment, determining the intensity of the light rays outputted from the outgoing core 9 and then adjusting the position of the diffraction grating 7 so that the intensity of the light rays is maximized to thus position the grating 7 .
- the wavelength ⁇ 5 herein used may be either of ⁇ 1 to ⁇ 4 . It is also possible to use either of the incident cores 4 as both the incident core 8 for alignment and the incident core 4 upon which either of light rays having wavelength of ⁇ 1 , ⁇ 2 , ⁇ 3 and ⁇ 4 is incident, when using a wavelength other than ⁇ 1 to ⁇ 4 as ⁇ 5 .
- light rays can be outputted from a specific outgoing core 5 corresponding to ⁇ 1 to ⁇ 4 , even if the wavelengths ⁇ 1 to ⁇ 4 of the incident light rays vary within predetermined wavelength ranges, respectively.
- FIG. 4( a ) is a side view of an optical waveguide according to the present invention
- FIG. 4( b ) is a cross sectional view thereof taken along the line A-A′ in FIG. 4( a ).
- a core 3 having a rectangular cross section is embedded in a cladding 2 positioned on a substrate 1 ; the core 3 has a pattern comprising four incident cores 4 , one outgoing core 5 , an incident core 8 and an outgoing core 9 for alignment and a slab-like core 6 ; and a diffraction grating 7 is arranged at the right edge of the optical waveguide.
- materials for preparing the substrate used herein may, for instance, be a glass, a semiconductor (Si or the like) or a polymeric resin.
- those for preparing the cladding 2 and the core 3 may be, for instance, SiO 2 , or SiO 2 which comprises at least one additive for controlling the refractive index of these cladding and core such as Ge, Ti and F, or a polymeric material such as a fluorinated polyimide, a silicone resin or an epoxy resin whose refractive index is adjusted.
- the diffraction grating 7 is provided, on the surface, with unevenness having a desired period and a metal such as Au or Al is coated on the surface thereof, which comes in contact with the optical waveguide, in order to reflect light rays.
- the optical waveguide of the present invention having the foregoing structure can be used as an optical multiplexer.
- Four kinds of light rays having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 and ⁇ 4 are incident upon the four incident cores 4 , respectively as shown in FIG. 4 .
- the incident light rays propagate through the incident cores 4 and the slab-like core 6 , they strike on the diffraction grating 7 , each light ray is reflected by the same at an angle specified by the wavelength thereof, the light rays having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 and ⁇ 4 are incident upon a predetermined single outgoing core 5 and the four kinds of light rays reflected by the diffraction grating 7 are externally outputted through the single outgoing core 5 .
- the resulting optical waveguide can operate as an optical multiplexer.
- the width of the outgoing core 5 is greater than that of the incident core 4 and more specifically, the width of each incident core 4 is 7 ⁇ m and that of the outgoing core 5 is 30 ⁇ m.
- an incident core 8 and an outgoing core 9 for the alignment of the diffraction grating 7 are formed in addition to the incident cores 4 and the outgoing cores 5 . They are used for accurately arranging the diffraction grating 7 at a predetermined position.
- Light rays having a wavelength of ⁇ 5 are incident upon the incident core 8 for alignment, followed by receiving the light rays reflected by the diffraction grating 7 on the outgoing core 9 for alignment, determining the intensity of the light rays outputted from the outgoing core 9 and then adjusting the position of the diffraction grating 7 so that the intensity of the light rays is maximized to thus align the grating 7 .
- the wavelength ⁇ 5 herein used may be either of ⁇ 1 to ⁇ 4 .
- either of the incident cores 4 as both the incident core 8 for alignment and the incident core 4 upon which either of light rays having wavelength of ⁇ 1 , ⁇ 2 , ⁇ 3 and ⁇ 4 is incident, when using a wavelength other than ⁇ 1 to ⁇ 4 as ⁇ 5 .
- light rays having wavelengths ⁇ 1 to ⁇ 4 can be outputted from the outgoing core 5 , even if the wavelengths ⁇ 1 to ⁇ 4 of the incident light rays vary within predetermined wavelength ranges, respectively.
- FIG. 6( a ) is a schematic side view of an optical waveguide according to the present invention
- FIG. 6( b ) is a cross sectional view thereof taken along the line A-A′ in FIG. 6( a ).
- a core 3 having a rectangular cross section is embedded in a cladding 2 positioned on a substrate 1 ; the core 3 has a pattern comprising one incident core 4 , four outgoing cores 5 , an incident core 8 and an outgoing core 9 for alignment and a slab-like core 6 ; and a diffraction grating 7 is arranged at the right edge of the optical waveguide.
- materials for preparing the substrate 1 used herein may, for instance, be a glass, a semiconductor (Si or the like) or a polymeric resin.
- those for preparing the cladding 2 and the core 3 may be, for instance, SiO 2 , or SiO 2 which comprises at least one additive for controlling the refractive index of these cladding and core such as Ge, Ti and F, or a polymeric material such as a fluorinated polyimide, a silicone resin or an epoxy resin whose refractive index is adjusted.
- the diffraction grating 7 is provided, on the surface, with unevenness having a desired period and a metal such as Au or Al is coated on the surface thereof, which comes in contact with the optical waveguide, in order to reflect light rays.
- the optical waveguide of the present invention having the foregoing structure can be used as an optical demultiplexer.
- the multiplexer-demultiplexer is used as a demultiplexer, four kinds of wavelength-multiplexed optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 and ⁇ 4 are incident upon a predetermined incident core 4 as shown in FIG. 6 .
- the incident light rays propagate through the incident core 4 and the slab-like core 6 , they strike on the diffraction grating 7 , each light ray is reflected by the same at an angle specified by the wavelength thereof, the light rays are divided into groups each having a wavelength of ⁇ 1 , ⁇ 2 , ⁇ 3 or ⁇ 4 , each of them is incident upon either of the corresponding outgoing cores 5 and the four kinds of light rays reflected by the diffraction grating 7 are externally outputted through the four outgoing cores 5 .
- the resulting optical waveguide can operate as an optical demultiplexer.
- the width of the outgoing core 5 is greater than that of the incident core 4 and more specifically, the width of the incident core 4 is 7 ⁇ m and that of each outgoing core 5 is 30 ⁇ m.
- an incident core 8 and an outgoing core 9 for the alignment of the diffraction grating 7 are formed in addition to the incident core 4 and the outgoing cores 5 . They are used for accurately arranging the diffraction grating 7 at a predetermined position.
- Light rays having a wavelength of ⁇ 5 are incident upon the incident core 8 for alignment, followed by receiving the light rays reflected by the diffraction grating 7 on the outgoing core 9 for alignment, determining the intensity of the light rays outputted from the outgoing core 9 and then adjusting the position of the diffraction grating 7 so that the intensity of the light rays is maximized to thus align the diffraction grating 7 .
- the wavelength ⁇ 5 herein used may be either of ⁇ 1 to ⁇ 4 .
- the incident core 4 as both the incident core 8 for alignment and the incident core 4 upon which light rays having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 and ⁇ 4 are incident, when using a wavelength other than ⁇ 1 to ⁇ 4 as ⁇ 5 .
- light rays having wavelengths ⁇ 1 to ⁇ 4 can be outputted from the outgoing cores 5 , even if the wavelengths ⁇ 1 to ⁇ 4 of the incident light rays vary within predetermined wavelength ranges, respectively.
- FIG. 8 is a block diagram showing an optical waveguide of the present invention.
- the optical waveguide has such a structure that a core 3 having a rectangular cross section is embedded in a cladding 2 positioned on a substrate 1 .
- the core 3 has a pattern comprising four incident cores 4 , four outgoing cores 5 having a width greater than that of the incident core 4 , a slab-like core 6 and an array-like core 10 .
- This structure is one referred to as an array type optical waveguide-diffraction grating.
- the optical waveguide having the structure according to this embodiment of the invention can operate as a multiplexer-demultiplexer.
- four kinds of optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 and ⁇ 4 are incident upon the corresponding incident cores 4 .
- the incident light rays propagate through the incident cores 4 and incident upon the slab-like core 6 , they further propagate through the array-like core 10 and the slab-like core 6 and they are then incident upon one of the four outgoing cores 5 .
- the four kinds of light rays having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 and ⁇ 4 are multiplexed by making these light rays incident upon one outgoing core 5 and the resulting multiplexed light is outputted from the core 5 after the propagation thereof through the core 5 .
- the optical waveguide when using the optical waveguide as a demultiplexer, four kinds of wavelength-multiplexed optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 and ⁇ 4 are incident upon one of the four incident cores 4 .
- the light rays incident upon the same propagate through the incident core 4 , they are incident upon the slab-like core 6 , they further propagate through the array-like core 10 and the slab-like core 6 and they are then incident upon one of the outgoing cores 5 .
- the light rays are divided into groups each having a wavelength of ⁇ 1 , ⁇ 2 , ⁇ 3 or ⁇ 4 , each of them is incident upon either of the corresponding outgoing cores 5 and they are externally outputted through the four outgoing cores 5 after the propagation through the core.
- materials for preparing the substrate used herein may, for instance, be a glass, a semiconductor (Si or the like) or a polymeric resin.
- those for preparing the cladding 2 and the core 3 may be, for instance, SiO 2 , or SiO 2 which comprises at least one additive for controlling the refractive index of these cladding and core such as Ge, Ti and F, or a polymeric material such as a fluorinated polyimide, a silicone resin or an epoxy resin, whose refractive index is adjusted.
- the width of the outgoing core 5 is greater than that of the incident core 4 and more specifically, the width of each incident core 4 is 7 ⁇ m and that of each outgoing core 5 is 30 ⁇ m.
- light rays having wavelengths ⁇ 1 to ⁇ 4 can operate as an optical multiplexer-demultiplexer, even if the wavelengths ⁇ 1 to ⁇ 4 of the incident light rays vary within predetermined wavelength ranges, respectively.
- FIG. 10( a ) is a block diagram showing an example of the optical multiplexer-demultiplexer according to the present invention
- FIG. 10( b ) is a cross sectional view thereof taken along the line A-A′ in FIG. 10( a )
- FIG. 10( c ) is a cross sectional view thereof taken along the line B-B′ in FIG. 10( a ).
- the device as shown in FIG. 10 is an example which makes use of a reflection type diffraction grating 4 , but the present invention is likewise effective when using a transmission type diffraction grating.
- an acrylic resin, SiO 2 , or SiO 2 which comprises at least one additive for controlling the refractive index of the same such as Ge, Ti and F to control the birefringence index of the core layer 2 to a level of not more than 0.007.
- the birefringence index thereof can likewise be controlled to not more than 0.007 by the use of a substrate 5 made of a resin such as a polyimide even when using such a core layer 2 for the optical waveguide prepared from a material having a high birefringence index such as a fluorinated polyimide.
- FIG. 11 is a diagram showing the fact that a multiplexed incident signal light is demultiplexed into a plurality of light rays by the action of the diffraction grating and then they are outputted through ports CH 1 to CH 4 or showing the optical demultiplexing characteristics observed for the optical multiplexer-demultiplexer shown in FIG. 10 .
- Such an embodiment having the foregoing structure would permit the control of the birefringence index of the layer to not more than 0.007 and the control of the wavelength fluctuation of the outputted signal light as shown in FIG. 11 to a level of not more than 5 nm.
- any occurrence of wavelength fluctuation can be suppressed by the reduction of the birefringence index of the core layer of an optical waveguide.
- the birefringence index of the resulting film was found to be not more than 0.001 at a wavelength of 1300 nm.
- an optical multiplexer-demultiplexer can be obtained by combining an optical waveguide which is prepared by forming, on an Si substrate, a core layer for an optical waveguide using this poly(methyl methacrylate) and a cladding layer therefor using a poly(fluoroalkyl methacrylate) whose refractive index is adjusted by the fluorination thereof, with a diffraction grating prepared using quartz as a basic material and the wavelength fluctuation of the device can thus be controlled to a level of not more than 1 nm.
- An optical multiplexer-demultiplexer was prepared by combining an optical waveguide (the birefringence index of the core layer thereof was 0.009 at a wavelength of 1300 nm) which was prepared by forming, on an Si substrate, a core layer for an optical waveguide using OPI-N3265 (a fluorinated polyimide resin available from Hitachi Chemical Co., Ltd.) and a cladding layer therefor using OPI-N3115 (a fluorinated polyimide resin available from Hitachi Chemical Co., Ltd.), with a diffraction grating prepared using quartz as a basic material, followed by the determination of the relation between the polarization direction and the optical demultiplexing characteristics of the resulting optical multiplexer-demultiplexer.
- OPI-N3265 a fluorinated polyimide resin available from Hitachi Chemical Co., Ltd.
- OPI-N3115 a fluorinated polyimide resin available from Hitachi Chemical Co., Ltd.
- the optical demultiplexing characteristics of the resulting device underwent a change depending on whether the signal light incident upon the optical waveguide was TE-polarized or TM-polarized one and this resulted in the generation of a wavelength fluctuation of 8 nm.
- This wavelength fluctuation is in good agreement with the value determined by the foregoing equation (1).
- the present invention permits the preparation of an optical waveguide used in an optical multiplexer-demultiplexer which can multiplex or demultiplex a plurality of light rays having different wavelengths each of which undergoes a change within a predetermined range. Moreover, the present invention also permits the preparation of an optical multiplexer-demultiplexer which can be used in the wavelength division multiplexing communication and more specifically, an optical multiplexer-demultiplexer in which the birefringence index of the core layer of the optical waveguide is controlled to a level of not more than 0.007 to thus control the wavelength fluctuation of the outputted signal light dependent on the polarization direction of the incident signal light to not more than 5 nm.
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Abstract
Description
Δλ=λ×Δn/n (1)
(10) An optical multiplexer-demultiplexer which makes use of an optical waveguide serving as an optical path and a diffraction grating for demultiplexing and focusing light, wherein the absolute value of the difference between the refractive index (nTE) of the core layer of the optical waveguide in the direction parallel to the plane of the film and that (nTM) of the core layer thereof in the direction perpendicular to the plane of the film is not more than 0.007 at the wavelength used.
(11) The optical multiplexer-demultiplexer as set forth in any one of the foregoing
Claims (19)
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
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JP2002091783 | 2002-03-28 | ||
JP2002-91783 | 2002-03-28 | ||
JP2002295375 | 2002-10-08 | ||
JP2002-295375 | 2002-10-08 | ||
PCT/JP2003/003820 WO2003083535A1 (en) | 2002-03-28 | 2003-03-27 | Optical waveguide and optical multiplexer/demultiplexer |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/JP2003/003820 Continuation WO2003083535A1 (en) | 2002-03-28 | 2003-03-27 | Optical waveguide and optical multiplexer/demultiplexer |
Publications (2)
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US20050041918A1 US20050041918A1 (en) | 2005-02-24 |
US7606493B2 true US7606493B2 (en) | 2009-10-20 |
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US10/949,657 Expired - Fee Related US7606493B2 (en) | 2002-03-28 | 2004-09-27 | Optical waveguide and optical multiplexer-demultiplexer |
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US (1) | US7606493B2 (en) |
JP (1) | JP4123519B2 (en) |
KR (1) | KR100695769B1 (en) |
CN (1) | CN1318868C (en) |
AU (1) | AU2003227262A1 (en) |
WO (1) | WO2003083535A1 (en) |
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TWI372465B (en) * | 2007-09-28 | 2012-09-11 | Chimei Innolux Corp | Image display system and fabrication method thereof |
KR101181991B1 (en) | 2011-01-07 | 2012-09-11 | 호남대학교 산학협력단 | plastic optical fiber coupler |
JP6384860B2 (en) * | 2014-07-31 | 2018-09-05 | 日東電工株式会社 | Optical waveguide and position sensor using the same |
US11335774B2 (en) * | 2019-10-18 | 2022-05-17 | Taiwan Semiconductor Manufacturing Company, Ltd. | Contact structure for semiconductor device and method |
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2003
- 2003-03-27 KR KR1020047015104A patent/KR100695769B1/en not_active IP Right Cessation
- 2003-03-27 CN CNB038070855A patent/CN1318868C/en not_active Expired - Fee Related
- 2003-03-27 AU AU2003227262A patent/AU2003227262A1/en not_active Abandoned
- 2003-03-27 JP JP2003580912A patent/JP4123519B2/en not_active Expired - Fee Related
- 2003-03-27 WO PCT/JP2003/003820 patent/WO2003083535A1/en active Application Filing
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2004
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Also Published As
Publication number | Publication date |
---|---|
JP4123519B2 (en) | 2008-07-23 |
CN1643417A (en) | 2005-07-20 |
CN1318868C (en) | 2007-05-30 |
KR20040097213A (en) | 2004-11-17 |
JPWO2003083535A1 (en) | 2005-08-04 |
AU2003227262A1 (en) | 2003-10-13 |
WO2003083535A1 (en) | 2003-10-09 |
US20050041918A1 (en) | 2005-02-24 |
KR100695769B1 (en) | 2007-03-15 |
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